• Journal of Korean Society of Environmental Engineers
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• v.35 no.6
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• pp.407-414
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• 2013

Full scale livestock wastewater treatment plant (100 t/d) was constructed and operated to develop compact and cost effective treatment process for public plant as well as individual farm. Liquid form of livestock wastewater after belt press filter was treated through MBR/NF/RO. NF/RO brine water was mixed with livestock wastewater sludge and treated using denitrification, coagulation and air flotation process. Mixed effluent of NF/RO and air flotation meet public livestock wastewater treatment standard, BOD, T-N and T-P, 30 mg/L, 60 mg/L, 8 mg/L below, respectively. Condensed sludge of air flotation returned belt press filter. Dewatered cake contained 90% water and could be used fertilizer after mixing sawdust.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.527-536
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• 2010

Although the bubble-floc agglomerate floated and formed the float layer on the surface of the water in the DAF process, after inducing in the thickening tank a part of the bubble-floc agglomerate come up again to the surface and the other is settled at the bottom of the tank. The bubble-floc agglomerate divided into two group as the scum on the surface and the sludge of the bottom gives rise to operational troubles for the thickening process. In order to find out the cause of break-up and the effective thickening method for sludge from the DAF process, the composition of the bubble-floc agglomerate was investigated and a series of flotation experiments carried out. There was no difference of composition between the scum on the surface and the sludge of the bottom in the thickening tank. The coagulation was not effective to improve the trouble that the bubble-floc agglomerate divided into the scum and the sludge. It was estimated that for the bubble-floc agglomerate of thickening tank the trouble was caused by not the change or the difference of chemical composition but whether the bubble-floc agglomerate hold bubbles. Furthermore, for the effective thickening of sludge from the DAF process, it is required an additional flotation applied the AS ratio depending upon the solid concentration of sludge as the operation parameter.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.191-200
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• 2004

DAF process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when the freshwater blooms occut or raw water turbidity become high. Pre-sedimentation iS prepared in case when raw water turbidity is very high by rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while it is difficult to remove in sedimentation. One of the main concerns in adoption of DAF (Dissolved Air-Flotation) process is a high raw water turbidity problem. That is, DAF is not adequate for raw water, which is more turbid than 100NTU. In order to avoid this problem, pre-sedimentation basins are prepared in DAF plant to decrease the turbidity of DAF influent. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, DAF process coupled with sedimentation is suggested that pre-sedimentation with optimum coagulation prior to DAF would be appropriate.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.267-276
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• 2010

Many plants have been improved to adapt the target of the biological treatment processes changed from organics to nutrients since the water quality criteria of effluent was reinforced and included T-N and T-P for the municipal wastewater treatment plant. To meet the criteria of T-N and T-P, the conventional biological reactor such as aeration tank in activated sludge system is changed to the BNR (biological nutrient removal) processes, which are typically divided into three units as anaerobic, anoxic and oxic tank. Therefore, the solid separation process should be redesigned to fit the BNR processes in case of the application of the DAF (dissolved air flotation) process as an alternatives because the solid-liquid separation characteristics of microbial flocs produced in the BNR processes are also different from that of activated sludge system as well. The results of this study revealed that the microbial floc of the anaerobic tank was the hardest to be separated among the three steps of the unit tanks for the BNR processes. On the contrary, the oxic tank was best for the removal efficiency of nutrients as well as suspended solid. In addition, the removal efficiency of nutrients was much improved under the chemical coagulation treatment though coagulation was not indispensable with a respect to the solid separation. On the other hand, in spited that the separation time for the microbial floc from the BNR processes were similar to the typical particles like clay flocs, over $2.32{\times}10^3$ ppm of air volume concentration was required to keep back the break-up of the bubble-floc agglomerates.

• Environmental Engineering Research
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• v.14 no.4
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• pp.220-225
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• 2009

The water quality in eutrophic lakes is affected by serious problems, such as abnormal increasing of Cyanobacteria. The purpose of this study was to investigate the possibility of a modified flotation system using a hybrid technique formed by chemical compounds and an electrostatic bridge. Therefore, experiments using the hybrid technique were performed to measure the zeta potential value on the phytoplankton surface and the removal efficiencies of phytoplankton, ammonia nitrogen, nitrate nitrogen and phosphoric acid. The results were as follows: Firstly, the zeta potential of M.aeruginosa was observed to approach charge neutralization due to adhesion of magnesium hydroxide precipitate on the phytoplankton surface in the pH range 10.5 to 11. Secondly, the concentration of chlorophyll-a decreased from about 150 to 20${\mu}g$g/L, with a maximum removal efficiency of 84% due to coagulation with pH values higher than 10. Thirdly, the N$H_4$-N concentration was observed to decrease from 0.62 to 0.54mg-N/L (13%), and the P$O_4$-P concentration, which is a limiting factor to the formation of algae blooms, decreased from 0.27 to 0.02mg-P/L (92%). These findings suggest that the modified flotation system can be applied for the purification of the raw water of numerous lakes containing high phytoplankton populations and elevated pH.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.415-419
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• 2017

In recent years there have been large increases in the hydraulic loading rates used to design dissolved air flotation (DAF) facilities for drinking water applications. High rate DAF processes are now available at loading rates of 20 to $40m^3/m^2{\cdot}h$. This research evaluated dissolved air flotation as a separation method for algae and organic compounds from water treatment plants. During the service period of 2016. 5. to 2017. 6., DAF pilot plants ($500m^3/day$) process has shown a constantly sound performance for the treatment of raw water, yielding a significantly low level of turbidity (DAF treated water, 0.21~1.56 NTU). As a result of analyzing the algae cell counts in the influent source, it was expressed at 100-120 cells/mL. In DAF treated water, the removal efficient of alge cell counts was found to be upto 90%. The stable turbidity and algae removal were confirmed by operating the high rate DAF process under the condition of the surface loading rate of $30m^3/m^2{\cdot}hr$.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.2
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• pp.24-33
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• 2015

This study aims to suggest wastewater treatment options for diaper recycling by identifying characteristic analysis of wastewater from diaper recycling process and efficiency evaluation of wastewater treatment units. The wastewater characteristic analysis showed that the concentration of organic pollutants and ionic materials were very high comparing to seawater. Through the investigation of similar wastewater treatment, six treatment units were identified to reduce pollutants. It is found UF(ultra-filtration), DAF(dissolved air flotation), fenton oxidation, electro-coagulation and chemical-coagulation are effective in reducing organic pollutants while membrane system and ion exchanger are effective in reducing ionic materials. Even though the target of water quality should be secured in terms of managing organic pollutants level, the application of treatment unit for reducing ionic material needs lots of considerations. This result suggests that reuse of pulping wastewater after controlling organic pollutants is better than direct discharge of pulping wastewater. To select the appropriate wastewater treatment unit, an economic analysis about operation condition, wastewater flow, cost, efficiency should be considered.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.861-867
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• 2011

Wastewater from crude oil reserve base usually contains large amount of non-biodegradable contaminants. The conventional wastewater treatment progress can hardly meet the regulation of wastewater effluent quality. This study investigated the removal of non-biodegradable organic contaminants in wastewater from crude oil reserve base using a pulse UV treatment. The modified process incorporating pulse UV process was set up to treat the wastewater from crude oil reserve base. The treatment process is composed with coagulation and flocculation, micro-bubble flotation, sand filter, pulse UV system, and GAC filter. The results show CODMn was effectively removed by the process with pulse UV system and it can meet the wastewater effluent regulation. The single effect of pulse UV process in CODMn removal was not significant(9~15% based on sand filtered effluent), however with the subsequent activated carbon filter the removal ratio CODMn was increased up to 28% compared to the process without pulse UV syetem.

• Journal of Environmental Science International
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• v.25 no.3
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• pp.425-438
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• 2016

This study carried out zeta potential measurements of the Microcystis sp. under various solutions condition and investigated the characteristics of Microcystis sp. through the size control of microbubbles to eliminate algae that causes problems in aquatic ecosystems and human activities. DAF process was adopted and several coagulants were used to remove the Microcystis sp. CCD Camera was used to measure and analyze the size of microbubble, and fluorescent microscope was used to observe the particle, algae species and community. Zeta potential behavior of the algae was analyzed by using ELS-Z. Lab-scale and pilot-scale experiments were conducted to test flotation process. Polyaluminium chloride(PAC) coagulant was used, and the removal efficiency of the algae was assessed through Chlorophyll-a analysis. In the Lab-scale experiment, 2.2 ppm, 11 ppm, 22 ppm, and 44 ppm of polyaluminium chloride was injected to coagulate the algae. The coagulated algae was floated by the microbubble. The microbubbles in the experiments were generated at a air pressure of 450 ~ 550 kPa. The microbubble size was controlled in $36{\mu}m$, $100{\mu}m$, and $200{\mu}m$, respectively by using different diffuser. The results of lab-scale experiments on flotation plant indicated that the average removal rate was about 90% or above for 11 ppm, 22 ppm, and 44 ppm of polyaluminium chloride. On the other hand, in the pilot-scale experiment, the removal efficiency was in the range of 85% to 95% in all dose ranges of polyalumium chloride and aluminium sulfate coagulants.

• Journal of Environmental Impact Assessment
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• v.28 no.3
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• pp.332-345
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• 2019

The purpose of the study is to evaluate the treatability of contaminated groundwater with TPH and (or) $Cr^{6+}$. Laboratory scale tests were performed for oil/water separation, dissolved air flotation (DAF), coagulation and precipitation, and filtration with sand and activated carbon respectively. Two times of oil/water separation tests for total 40 minutes of separation or separating time shows 90.2 % of TPH removal rate. In case of DAF test for high TPH sample, the TPH removal rates were not varied significantly by the variation of microbubble size. However, tests for low TPH samples show that TPH removal rate increases as microbubbles are smaller. When coagulant was added to sample for DAF test, TPH removal rate was increased 12.3 %. SS removal rate by DAF was 97.9 % at $16-40{\mu}m$ and it was increased as the size of microbubble is reduced. Tests for coagulation and precipitation were performed to evaluate the removal of $Cr^{6+}$ in groundwater. The increase of $FeSO_4$ dosage increased $Cr^{6+}$ removal rate in the coagulation and precipitation process. As the amount of activated carbon in the filter media increased TPH removal rate in the filtration process. SS removal rate by the filtration was 96.7 % similar to the results of DAF process tests. The filtration process treats TPH and SS. Best design parameters are determined as the size of sand is $425-850{\mu}m$ and the ratio of activated carbon and sand is 50:50.